The steroid androstenedione is the direct precursor to testosterone in the synthetic pathway of androgens. Androstenedione is marketed as a "dietary supplement" in oral formulation and sold without prescription. It purported beneficial effects include increasing muscle mass, enhancing athletic performance, and improving sense of well being. The goal of this study is to determine if orally administered androstenedione, when given in standard doses to normal male volunteers for seven days, raises sex steroid levels or suppresses gonadotropins. Normal men ages 20 - 40 will be randomized to receive either 100 mg, 300 mg, or 0 mg (control) of androstenedione for seven days. Detailed pharmokinetic measurements of multiple sex-steroids over 8 hours will be performed on days 1 and 7. On days 2 - 6, baseline and 120 minute samples will be drawn. Gonadtropin levels will be measured daily along with standard chemistries and liver function tests. These measures will allow us to determine if androstenedione is converted to potent androgens or estrogens, suppresses normal feedback of gonadal function or is associated with any short term toxicity.